The present invention relates to a radiation monitor that is provided in radiation utilization facilities, facilities requiring radiation protection, or the like so as to monitor radiation and a method for checking operation of the same and, more particularly, to a radiation monitor provided with an operation check function using an optical pulse and a method for checking operation of the same.
As a commonly-used radiation monitor, there is known a semiconductor type radiation monitor using a detection element obtained by giving sensitivity with respect to radiation to the p-n junction of a diode in a sensor section. The semiconductor type radiation monitor includes a radiation source in the sensor section in order to check whether the sensor section is normally operating. However, it is assumed from now on that regulation on handling of radioactive materials is made stricter, so that a radiation monitor that can check soundness of the operation of the sensor section without using a radiation source is required. The same can be said for other detection elements, such as those using a scintillator or photomultiplier.
In response to the above demand, a configuration in which an LED (Light Emitting Diode) is used in place of the radiation source is adopted. This configuration is achieved by using characteristics that the detection element has sensitivity with respect also to light. Meanwhile, in a detection element using a semiconductor, inappropriate reverse bias voltage may cause sensitivity, resulting in a false detection. In order to cope with this problem, there is proposed the following method. In this method, an LED is caused to emit optical pulses so as to obtain an output similar to the radiation, and the optical pulses are allowed to irradiate the detection element with the repetition frequency of the optical pulses controlled so as to perform operation check. Through this operation check, presence/absence of abnormality in reverse bias voltage is determined to thereby check the soundness of the operation of the sensor section (refer to, e.g., Japanese Patent Application Laid-Open Publication No. 02-128184, the entire content of which is incorporated herein by reference).
As described above, the above prior art is configured to detect the abnormality in the bias voltage by using an LED. Further, at present, strongly desired is a configuration capable of performing check of the soundness of the sensor section at any time, without influencing radiation measurement, from a monitor module section remotely installed from the sensor section.